The present invention relates to a packaging tray suitable for permanently holding liquid exuding from a packaged article, which tray at least on and/or in its base wall has at least one cylindrical bulge which is open towards the interior of the packaging tray, the diameter of which, remaining constant over the entire depth of the bulge, being between 2 and 6 mm, and the depth of which being 1.5 times the diameter, and to a corresponding package.
The present invention also relates to a method of permanently separating a packaged article, such as a foodstuff, from liquid exuding therefrom by packaging the article in a packaging tray according to the invention, collecting and holding the liquid exuding from the packaged article in the bulges of the packaging tray of the invention, the total volume of the overall bulges in the packaging tray being required to correspond at least to the volume of the liquid to be collected, and to a correspondingly packaged article.
The preservation of foodstuffs is gaining more and more importance today. In addition to preservation by deep-freezing, foodstuffs are increasingly packaged in preferably gas-tight films. It is particularly important in this type of package that the packaged articles such as meat, fish and/or vegetables be separated as completely as possible from liquid exuding therefrom during storage, because microorganisms tend to grow in such a liquid, initiating a putrefaction process of the packaged foodstuffs.
In the past, attempts have been made to absorb these liquids, such as water, blood and/or cell plasma, in absorbent fleeces inserted between the packaged article and the packaging tray.
This procedure is disadvantageous in that, on the one hand, the packaged article is not actually separated from the exuded liquid, because the article is lying on the fleece having absorbed the liquid. On the other hand, the fleece soaked with liquid, frequently adhering to the packaged article, does not present an optically attractive view for a consumer.
It was therefore the object to provide a package which collects the liquid exuding from the packaged article, permanently separating it from the packaged article during the time of storage, and does not involve the above-described drawbacks.
According to the invention, said object is solved by providing a packaging tray which at least on and/or in its base wall has at least one cylindrical bulge which is open towards the interior of the packaging tray, the diameter of which, remaining constant over the entire depth of the bulge, being between 2 and 6 mm, and the depth of which being 1.5 times the diameter.
The minimum number of bulges is estimated according to the expected amount of liquid exuding from the packaged article. Said amount of liquid is determined according to methods for determining the percentage of moisture in the article to be packaged, which are common for a person skilled in the art.
However, the total volume of the bulges preferably is by 50-60% larger than the volume of exuded liquid expected in order to ensure separation of the liquid from the packaged article.
Undesirable liquid is retained by capillary action in the bulges of the packaging tray according to the invention. The maximum possible diameter of a bulge depends on the surface tension between the packaging material and the liquid to be retained and may be determined using a well-known, easy measurement.
It is preferred to arrange the bulges at regular spacings on and/or in the packaging tray, and the bulges may be arranged both on the base wall and the side walls of the packaging tray.
However, it is particularly preferred to arrange the bulges on and/or in the base wall of the packaging tray.
In this fashion, the bulges may also serve as feet for the packaging tray and therefore, they must be arranged such that the packaging tray is in a horizontal position thereon.
The packaging tray of the invention is preferably made of thermoplastic polymer materials common in packaging foodstuffs, such as polypropylenes, polyethylenes, polyesters, polycarbonates, polyethylene naphthalates, or polystyrenes. Deep-drawable and dimensionally stable single-layer or multilayer films are particularly suited for producing such a packaging tray.
It is highly preferred to produce the packaging tray from a foamed film based on polypropylene, the use of a high melt strength polypropylene being particularly preferred.
High melt strength polypropylenes are manufactured by the Himont Company, for example, and may be mixed with conventional polypropylenes in a ratio of 1:1.
The polypropylene is optionally mixed with a copolymer of propylene and ethylene. The ethylene percentage of the copolymer is between 1 and 10 wt.-%.
The packaging tray is preferably produced from a multilayered film containing functional layers. On the one hand, functional layers are common barrier layers having low permeability for oxygen, nitrogen, carbon dioxide, and/or water vapor, and on the other hand, the well-known sealing layers and primer layers.
It is particularly preferred to produce the packaging tray from a multilayered barrier film having the following structure:
A A foamed support layer produced from a mixture of 50 wt.-% of a high melt strength polypropylene and 50 wt.-% of a conventional polypropylene, or a copolymer of propylene and ethylene, the ethylene percentage being 1-10 wt.-%. The polypropylene is foamed using a chemical or physical blowing agent. The thickness of the foamed layer is between 500 and 800 xcexcm.
B A thermoplastic primer layer joining the layers A and C.
C A five-layered film which is structured as follows:
a polypropylene layer
a primer layer
a barrier layer made of polyethylene vinyl alcohol (including about 35 wt.-% of vinyl alcohol),
a primer layer
a sealing layer made of low density polyethylene (LDPE), or a peelable sealing layer made of a mixture of LDPE and polybutylene.
Following filling, the packaging trays of the invention, produced by thermoforming, preferably by deep-drawing, are preferably sealed with well-known cover films which may be multilayered films having a layer sequence of, e.g., polyethylene terephthalate (PET), poly(vinylidene chloride) (PVDC)/adhesive/LDPE or PET/adhesive//PE/primer/EVOH/primer/PE.
Films having the structure PET/SiOx//adhesive//LDPE are particularly suited as cover films. Such a film is remarkable for its particularly high transparency and a high cross-breaking resistance. A package tray sealed therewith has a particularly high gas barrier.
Using the packaging tray of the invention, it is possible to permanently separate the packaged article fromxe2x80x94mostly aqueousxe2x80x94liquid exuding therefrom and thus, keep the packaged article dry even upon prolonged storage.
Therefore, the present invention is also directed to a method of permanently separating a packaged article from liquid exuding therefrom by packaging the article in a packaging tray according to the invention, the exuding liquid being collected in the bulges thereof and retained therein, the total volume of said bulges being required to correspond at least to the volume of the liquid to be collected.
However, the total volume of the bulges is preferably dimensioned to be  greater than 50% of the expected volume of liquid exuding from the packaged article.
The volume of the liquid exuding from the packaged article can be estimated on the basis of amount, type and quality of the packaged article. For a more precise determination of the amount of liquid to be collected, well-known methods such as those used in food chemistry to determine the amount of moisture may be utilized.
In the package according to the invention, meat (fresh), fish and/or vegetables can be stored in packaged condition, permanently separated from exuding liquid which is aqueous in most cases, such as water, blood and/or cell plasma.
Inter alia, one advantage of the package according to the invention therefore is that the packaged article remains permanently separated from liquid exuding therefrom. As a result, the packages and/or the packaged articles are optically more attractive and more durable.